Character appearing in Chapter One (3)
I believe the answer is:
chi
'character' is the definition.
(chi is a kind of character)
'chapter one' is the wordplay.
'chapter' becomes 'ch'.
'one' becomes 'i' (Roman numeral**).
'ch'+'i'='CHI'
'appearing in' is the link.
(Other definitions for chi that I've seen before include "T'ai -, martial art" , "The 22nd letter of Greek alphabet" , "In Chinese medicine, the life force inherent in all things" , "Greek letter; Chinese life force" , "Twenty-second Greek letter" .)